Handle ProcessChain in open(f, cmd, ..) (#49166)

Author: hexaeder

base/process.jl

@@ -413,7 +413,7 @@ process failed, or if the process attempts to print anything to stdout.
 """
 function open(f::Function, cmds::AbstractCmd, args...; kwargs...)
     P = open(cmds, args...; kwargs...)
-    function waitkill(P::Process)
+    function waitkill(P::Union{Process,ProcessChain})
         close(P)
         # 0.1 seconds after we hope it dies (from closing stdio),
         # we kill the process with SIGTERM (15)